1. Field of the Invention
The present invention concerns a one-piece battery incorporating a circulating fluid type heat exchanger.
2. Description of the Prior Art
The electrode assemblies of a one-piece battery are contained in cells of a single container. The container is usually prism-shaped. Each electrode assembly comprises alternating positive and negative electrodes separated from each other by a separator and impregnated with an electrolyte. The electrode assembly has two relatively smaller faces corresponding to the edges of the stacked electrodes and two relatively larger faces parallel to the surfaces of the electrodes.
Such batteries are used in particular to power electric vehicles. A one-piece nickel-cadmium or nickel-metal hydride battery has a capacity in the range from 5 Ah to 250 Ah.
The various states of use of a storage battery (charging, overcharging, discharging) are known to raise its temperature, which modifies its performance. The most effective way to cool the battery is to remove the heat using a circulating fluid, in particular a heat exchange fluid. Many heat exchangers have been proposed that are independent of the battery and placed in contact with it. Most such systems increase the weight and overall size of the battery to an unacceptable degree.
A one-piece battery including a compact cooling system has recently been proposed. The battery has a single prism-shaped plastics material container consisting of a tank and a lid carrying the terminals. The tank includes cells in which the electrode assemblies are placed separated by partitions. The cooling system includes two flanges welded and sealed to respective opposite walls of the plastics material tank. Each flange defines with the corresponding wall a circulation compartment for the liquid having at the top an inlet orifice and an outlet orifice leading into the lid of the battery.
For the electrode assemblies to be uniformly cooled, a system of the above kind is preferably placed on the walls of the tank facing the edges of the electrodes. In the case of high-power batteries, cooling the edges of the electrodes is insufficient to maintain the battery at a suitable temperature. To increase the heat exchange area it is therefore necessary for the heat to be transferred via the wall facing the relatively larger faces of each assembly.
U.S. Pat. No. 5,356,735 describes a one-piece battery including a heat exchanger of the above kind and whose container comprises a single prism-shaped tank and a lid in several parts. The liquid circulation compartments are formed by two facing flanges. The compartments constitute partitions separating the cells. To this end the perimeter of the partitions is engaged in grooves formed on the walls of the tank. Each compartment is individually connected to an inlet/outlet manifold. To prevent the liquid entering the cells, a coupling unit nested in a housing provides communication between each compartment and the manifold. This complex assembly system has many joints, which makes it somewhat unreliable, in particular with regard to the risk of the heat exchange liquid leaking into the cells.
The liquid inlet and outlet of each compartment are connected to a common inlet and outlet by longitudinal manifolds formed in an attached lid. The two longitudinal manifolds clutter the lid. To compensate for this, the lid carries only two terminals for connecting the battery to an external circuit. This requires the use of an internal electrical connection arrangement that has to pass in a sealed manner through the partition separating two contiguous cells and comprising the liquid circulation compartment. Lead-through devices are not sufficiently reliable electrically or mechanically to be used in an electric vehicle.
Manifolds of increasing diameter are formed by joining two complementary parts of the lid, each carrying passages. The lid, formed of three superposed parts, fits onto the tank. For a battery comprising a given number of electrode assemblies, the dimensions of the various parts constituting the container are fixed. Accordingly, each battery of given capacity has its own specific components, which makes industrial manufacture less flexible and more costly.
The aim of the present invention is to propose a one-piece battery provided with a compact and effective heat exchanger and which is simpler to manufacture and more reliable than prior art systems.
Another aim of the present invention is to propose a one-piece battery provided with a heat exchanger and in which the number of electrode assemblies can easily be modified.